The invention generally relates to electrical technology and, more specifically, to a method and apparatus for diminishing grid complexity in a tablet.
Tablets are conventionally used to enter data, such as drawings or scripted text, into an electrical system, such as a computer. A user manipulates a transducer, such as a pen or a mouse, over the tablet to enter the data.
Tablets include complex grid patterns to accurately identify the position of the pointer on the tablet. U.S. Pat. No. 4,948,926 to Murakami et al., hereby incorporated by reference, illustrates an exemplary complex grid pattern.
Complex grid patterns are undesirable because they employ more grid lines, more internal and external interconnections and more selection multiplexers and other circuitry to operate them. Numerous lines and interconnections require narrower lines and less space between them and, therefore, require more elaborate and expensive grid processes and materials, such as etched copper on epoxy fiberglass, in contrast to less expensive, but less detailed, printed methods such as silver ink on Mylar(copyright) sheet. Therefore, there is a need for less complex and less expensive grid patterns, and their corresponding position resolving algorithms, that can accurately identify the position of a transducer, such as a pen or cursor, on a tablet or digitizer surface.
The invention solves the above-mentioned problems in the art and other problems which will be understood by those skilled in the art upon reading and understanding the specification. The invention provides a method and apparatus for diminishing grid complexity in a tablet. In all embodiments of the invention, reference to a transducer includes any device generating a magnetic-field including a pen, a cursor, a mouse, a puck or other related devices.
The invention provides a two-wire resolution grid, or antenna wire pattern, consisting of a first serpentine, and a second serpentine overlapping and substantially coplanar with the first serpentine. The second serpentine is offset from the first serpentine in the direction of the axes of the serpentines. Signals from the first and second serpentines are analyzed to determine transducer position within a period of a serpentine in the axis direction. In another embodiment, first and second serpentines are foldback serpentines. In yet another embodiment, the second serpentine is offset from the first serpentine by approximately ninety degrees, or approximately one quarter of one period. In one embodiment, the loop size of first and second serpentines is about one inch, resulting in a period of about two inches.
The two serpentine patterns operate together with signal processing algorithms, and their associated circuitry, to determine transducer position within a period to high dimensional accuracy. The signal pattern of one wire operates to compensate for the signal pattern of the other wire to increase linearity and, therefore, improve position resolution and accuracy. Additionally, the two-wire grid linearity helps optimize or minimize transducer tilt error, where tilting the transducer causes an undesired location change in the data.
These two-wire resolution grids are capable of determining fine position over an about two inch period when used with a pen transducer. This approximately two-inch resolution distance is limited by the signal strength and characteristics of existing pen transducers. Larger loop sizes can proportionally increase resolution distance when utilized with a cursor or other device having a larger diameter signal coil.
In one embodiment of the invention, loops of the serpentines of a resolution grid are rectangular. In a further embodiment, loops of the serpentines of a resolution grid are rounded. In yet another embodiment, loops of the serpentines of a resolution grid are angled.
In a further embodiment, the invention provides a three-wire resolution grid consisting of a first serpentine, a second serpentine overlapping and substantially coplanar with the first serpentine and a third serpentine overlapping and substantially coplanar with the first and second serpentines. The second serpentine is offset from the first serpentine in the direction of the axes of the serpentines. The third serpentine is offset from both the first and second serpentines in the direction of the axes of the serpentines. Signals from the serpentines are analyzed to determine transducer position within a period in the axis direction. Use of three wires improves linearity of the signal processing over a period of the resolution grid to increase feasible resolution distance relative to a two-wire resolution grid when used with a given transducer. As an example, if a two-wire grid is limited to a period of two inches due to transducer characteristics, a three-wire resolution grid would be capable of spanning a distance proportional to the number of wires, i.e., a period of three inches. In another embodiment, first, second and third serpentines are foldback serpentines. In yet another embodiment, the second serpentine is offset from the first serpentine by approximately sixty degrees and the third serpentine is offset from the first serpentine by approximately one hundred twenty degrees.
In a still further embodiment, the invention provides a multi-wire resolution grid comprising three or more overlapping and substantially coplanar serpentines. Each serpentine is offset from the first serpentine in the direction of the axes of the serpentines. Signals from the serpentines are analyzed to determine transducer position within a period of a serpentine in the axis direction. Use of three or more wires improves linearity of the signal processing over a period of the multi-wire resolution grid to increase feasible resolution distance relative to a resolution grid using fewer wires when used with a given transducer. As an example, if a three-wire grid is limited to a period of three inches due to transducer characteristics, a five-wire resolution grid would be capable of spanning a distance proportional to the number of wires, i.e., a period of five inches. In another embodiment, each serpentine is a foldback serpentine. In yet another embodiment, each serpentine is offset from other serpentines by an amount equal to approximately one hundred eighty degrees divided by the total number of serpentines.
In one embodiment, the invention provides a direction grid consisting of one two-wire resolution grid. The one two-wire resolution grid consists of one period of the first and second serpentines such that absolute transducer position is determinable in one dimension in the direction of the axis of the resolution grid. In a further embodiment, the first and second serpentines are foldback serpentines.
In another embodiment, the invention provides a directional grid consisting of two substantially coplanar resolution grids overlaid upon a substantially common axis. A first, or fine, resolution grid includes two or more periods. The fine resolution grid consists of a two-wire resolution grid. A second, or coarse, resolution grid includes one or more periods. The coarse resolution grid consists of a multi-wire resolution grid. The length of the period of the coarse resolution grid is greater than the length of the period of the fine resolution grid. The one or more periods of the coarse resolution grid substantially cover the multiple periods of the fine resolution grid. Relative position within a period of the fine resolution grid is compared to the relative position within a period of the coarse resolution grid such that the period of the fine resolution grid generating the signal can be determined and an absolute transducer position in one axis can be calculated. In this manner, accuracy can be defined by the period of the fine resolution grid while the coarse resolution grid allows determination of which period generated the signal. In yet another embodiment, the resolution grids are substantially concentric. In a further embodiment, the resolution grids comprise foldback serpentines.
Any resolution grid containing more than one period may include fractional periods. As an example, a fine resolution grid may contain four and one-half two-inch periods in use with a coarse resolution grid having three three-inch periods to cover substantially the same grid pattern area.
In a further embodiment, the invention provides a direction grid comprising a fine resolution grid and two or more coarse resolution grids. Each two or more coarse resolution grids overlay a portion of the fine resolution grid. The fine resolution grid consists of a two-wire resolution grid. The combined two or more coarse resolution grids substantially cover the multiple periods of the fine resolution grid. The coarse resolution grids overlay the fine resolution grid such that the coarse and fine resolution grids substantially share a common axis and plane, and the coarse resolution grids overlay substantially different portions of the fine resolution grid. Relative position within a period of the fine resolution grid is compared to the relative position within a period of a coarse resolution grid such that the period of the fine resolution grid generating the signal can be determined and an absolute transducer position in one axis can be calculated. In this manner, accuracy can be defined by the period of the fine resolution grid while the two or more coarse resolution grids allow determination of which period of the fine resolution grid generated the signal. In a still further embodiment, the coarse resolution grids are concentric. In yet another embodiment, the coarse resolution grids are segmented and substantially adjacent. In a still further embodiment, the periodic length of the segmented coarse resolution grids substantially equals the periodic length of the fine resolution grid, and one coarse resolution grid overlays each period of the fine resolution grid.
In yet another embodiment, the invention provides a directional grid comprising a fine resolution grid, a coarse resolution grid and a lateral resolution grid. The lateral resolution grid consists of a first foldback serpentine. The coarse resolution grid and lateral resolution grid overlay the fine resolution grid such that all grids substantially share a common axis and plane. The lateral resolution grid substantially covers the multiple periods of the fine resolution grid. Relative position within a period of the fine resolution grid is compared to the relative position within a period of the coarse resolution grid such that the period of the fine resolution grid generating the signal can be determined to be in one of two positions, each possible value occurring in different hemispheres of the grid plane. The lateral resolution grid allows determination of the hemisphere of the grid plane containing the period of the fine resolution grid generating the signal such that an absolute transducer position in one axis can be calculated. In this manner, accuracy can be defined by the period of the fine resolution grid while the coarse resolution grid and lateral resolution grid allow determination of which period of the fine resolution grid generated the signal. In still another embodiment of the invention, the lateral resolution grid further comprises one or more fragmented foldback serpentines. The one or more fragmented foldback serpentines of the lateral resolution grid overlay substantially different portions of the fine resolution grid, each being substantially concentric with the first foldback serpentine of the lateral resolution grid.
It should be noted that both the coarse and lateral resolution grids described provide primarily a gross positioning of the transducer location, while the fine resolution grid determines accuracy. Accordingly, both coarse and lateral resolution grids may hereinafter be described as gross resolution grids.
The invention also provides for a tablet comprising a first directional grid, or x-grid, and a second directional grid, or y-grid. The x-grid and y-grid each include one or more resolution grids. The x-grid and y-grid are overlaid and rotated about each other. Determination of absolute transducer position in one axis of each grid allows for a determination of absolute transducer position within the plane of the x-grid and y-grid. In another embodiment, the y-grid is substantially coplanar to, and rotated ninety degrees from, the x-grid.
In further embodiment, a tablet comprises an x-grid and a y-grid. An x-axis multiplexer is coupled to the x-grid. A y-axis multiplexer is coupled to the y-grid. An amplifier and filter is coupled to the x-axis and y-axis multiplexors. A synchronous detector is coupled to the amplifier and filter. An analog to digital (A/D) convertor is coupled to the synchronous detector. A NAND gate circuit is coupled to the A/D converter. A processor is coupled to the NAND gate circuit. A first level converter is coupled to the processor. A second level converter is coupled to the processor. The x-grid and y-grid each include a fine resolution grid and one or more gross resolution grids. Each fine resolution grid consists of a first serpentine and a second serpentine overlapping the first serpentine. Signals from the serpentines of the resolution grids are analyzed to determine transducer position.
In yet another embodiment, a system comprises a processor and a tablet coupled to the processor. The tablet includes an x-grid and a y-grid. An x-axis multiplexer is coupled to the x-grid. A y-axis multiplexer is coupled to the y-grid. An amplifier and filter is coupled to the x-axis and y-axis multiplexors. A synchronous detector is coupled to the amplifier and filter. An analog to digital (A/D) convertor is coupled to the synchronous detector. A NAND gate circuit is coupled to the A/D converter. A second processor is coupled to the NAND gate circuit. A first level converter is coupled to the second processor. A second level converter is coupled to the first and second processors. The x-grid and y-grid each include a fine resolution grid and one or more gross resolution grids. Each fine resolution grid consists of a first serpentine, and a second serpentine overlapping the first serpentine. The signals from the serpentines of the resolution grids are analyzed to determine transducer position. In another embodiment, one or more resolution grids comprise foldback serpentines.
In a still further embodiment, a system comprises a processor and a tablet coupled to the processor. The tablet includes an x-grid and a y-grid. An x-axis multiplexer is coupled to the x-grid. A y-axis multiplexer is coupled to the y-grid. An amplifier and filter is coupled to the x-axis and y-axis multiplexors. A synchronous detector is coupled to the amplifier and filter. An analog to digital (A/D) convertor is coupled to the synchronous detector. A NAND gate circuit is coupled to the A/D converter. A second processor is coupled to the NAND gate circuit. A first level converter is coupled to the second processor. A second level converter is coupled to the first and second processors. The x-grid and y-grid each include a fine resolution grid and one or more gross resolution grids. In another embodiment, one or more resolution grids comprise foldback serpentines.
In yet another embodiment, a system comprises a processor and a tablet coupled to the processor. The tablet includes an x-grid and a y-grid. An x-axis multiplexer is coupled to the x-grid. A y-axis multiplexer is coupled to the y-grid. An amplifier and filter is coupled to the x-axis and y-axis multiplexors. A synchronous detector is coupled to the amplifier and filter. An analog to digital (A/D) convertor is coupled to the synchronous detector. A NAND gate circuit is coupled to the A/D converter. A second processor is coupled to the NAND gate circuit. A first level converter is coupled to the second processor. A second level converter is coupled to the first and second processors. The x-grid and y-grid each include a fine resolution grid, a coarse resolution grid, and one or more gross resolution grids. In another embodiment, one or more resolution grids comprise foldback serpentines.
The total size of a resolution grid, direction grid, grid pattern or tablet of the invention is limited only by the size and number of serpentine periods and grid layers, and the practical limitations imposed by their electrical properties such as induction, capacitance, resistance and other properties.
In each embodiment, as will be apparent to those skilled in the art upon reading the specification, additional lines or resolution grids can be used around the edges to further expand the size of the tablet and to handle unique characteristics of the tablet associated with the boundary or edges.
It is an advantage of the invention that tablet cost and complexity is reduced, and grid accuracy is enhanced or maintained.